Did you know that hearing, light pulses, and touch can stimulate the same area of the brain?
It’s almost as if our brains can hear in different ways. Often a deaf individual’s brain will still use the auditory cortex—but in response to touch. This fascinating concept can give some insight into how both hearing and deaf people learn and communicate.
In my American Sign Language (ASL) fingerspelling class, I had an interesting experience with my own “hearing” of the language. About an hour into our session, I began losing focus—I felt myself drifting off while our Deaf instructor stood at my desk fingerspelling something. I completely missed it. She signed WATCH, indicating for me to focus. Once I gave my full attention, she signed THREE. Then she moved her hand ever so slightly higher and to the right, and she signed FOUR. Then, moving her hand slightly lower, she signed TWO.
AH! I saw the number 342! She explained to the class, “Your eyes get tired because you are not used to hearing with your eyes. It will get easier.”
The Brain’s Ability to Hear in Different Ways
In my interview with audiologist Angie Lederman, MS, CCC-A of Hear Now Audiology & Tinnitus Center, Angie and I talked about the Deaf person’s experience of auditory fatigue. Like the fatigue in a hearing person’s eyes—like what I had experienced in my class—the Deaf person experiences auditory fatigue. In her interview with the Guardian, Sara Novic said, “sometimes I turn off my hearing aids and dip below the surface of the sound.” This is because our brains adapt to the senses we have been given.
Evelyn Glennie is a musician who became deaf as a young girl—after her auditory cortex had already learned much about sound, especially music. She’d wanted to be a percussionist. Her story is told in a beautiful picture book, Listen: How Evelyn Glennie, a Deaf Girl, Changed Percussion by Shannon Stocker. Determined to play, Evelyn forged a way. Shannon writes the following about Evelyn’s audition for the Royal Academy of Music in London:
“If she could learn to think about listening in a whole new way, they [the Academy judges who turned her down] could too. Evelyn knew that sound and touch weren’t that different. The air vibrated, traveling through the judges’ ears before turning into sound. For Evelyn, those vibrations traveled through her body. Her brain just listened differently.”
How do our brains enable us to hear and see with different abilities? These accounts of hearing, seeing, and knowing are explained through research. Research by the National Institute on Deafness and Other Communication Disorders (NIDCD) through the National Institutes of Health (NIH) (2015) reports: “NIH study shows the deaf brain processes touch differently.” One researcher, Christina M. Karns, Ph.D., of the Brain Development Lab at the University of Oregon, and her colleagues tested the effects of touch and light stimuli on the auditory cortex. They found that “deaf people use the auditory cortex to process touch and visual stimuli to a much greater degree than occurs in hearing people.”
How Was It Tested?
In my blog article “Shannon Stocker Shares a Very Personal Story,” Shannon shares how Evelyn Glennie developed her auditory cortex to play percussion. Evelyn Glennie had been devastated by her hearing loss as a young girl. Fortunately, she’d had a music teacher who’d sent her home with a drum to play with all its parts and vibrations. Together, they had explored how Evelyn could use her whole body to hear all the vibrations the hearing person understands as sound.
Dr. Karns and her colleagues’ research showed that the auditory cortex of the deaf subjects’ brains responded to soundless puffs of air that touched the right eyebrow and the cheek below the right eye.
In their study, a magnetic resonance imaging (MRI) scanner recorded brain activity caused by air touching the face. In both hearing and deaf groups, visual stimuli were also tested with brief light pulses delivered through a cable mounted directly below the air-puff nozzle.
The research built on the prior knowledge of a perceptual illusion in hearing people. This visual illusion causes a hearing person to experience multiple flashes of light when exposed to two sounds accompanied by one flash of light. The study sought to discover how deaf participants would respond to a similar tactile stimulation.
Dr. Karns states, “We designed this study because we thought touch and vision might have stronger interactions in the auditory cortices of deaf people.” The experiment found that this was correct.
“The finding suggests that since the developing auditory cortex of profoundly deaf people is not exposed to sound stimuli, it adapts and takes on additional sensory processing tasks,” as stated in the NIH study.
